By Jay Lund

As the old saying goes, “Someone with one watch knows what time it is, someone with two watches is never sure.”

Water accounting is fundamental to water management, but is not easy.  But any accounting is more difficult and expensive if it is less organized.  To illustrate this point, let’s look at estimates of one of the largest, most important, and “easiest” to measure flows in California: the annual pumped quantity of California’s State Water Project (SWP) Banks Pumping Plant (Banks) in the Delta for the years 2006 through 2010.

Public sources for annual quantity of Banks delivery includes DWR and USBR sources and documentation.  Pumped water quantity estimates from these sources are shown in the table and chart below, with hyperlinks to sources.

Notes and Sources:

1. DWR State Water Project Annual Report of Operations, Table 1: Project Pumping by Plant, Calendar Year
2. USBR Central Valley Operations: Delta Operations Water Accounting Reports, (monthly sum, calendar year); Delta Pumping Plant: State/Fed Banks
3. DWR, DAYFLOW Program, Environmental Planning and Information Branch, water entering pumping plant’s Clifton Court Forebay, originally water year, here converted to calendar year
4. DWR Bulletin 132: Management of the California State Water Project (2014 Report) Table B-6: Annual Water Quantities Conveyed through Each Pumping Plant, pg. B-67, Calendar year
5. DWR State Water Project Final Delivery Capability Report (2014 Report) Tables 7-2 through 7-11: Historical SWP Deliveries, Calendar Year
6. DWR Bulletin 160: California Water Plan, Update 2013 Volume 5. Technical Guides, Water Portfolios. Data Summary 1998-2010, State Water Project Deliveries, by Water Year^ – Calendar year, unless otherwise specified
   # – Water Years represent the annual water cycle and run from October 1 through September 30 and are named for the calendar year in which they end.
   * DWR SWP Operations Control Office also releases weekly Summary of SWP Water Operations with year-to-date, month-to-date, and weekly pumping quantities. These data are not included as data are updated weekly with prior weeks’ data removed from site (e.g., ‘Water Pumped’ for Banks CDWR, Total).

DWR SWP Annual Reports of Operations, Bulletin 132 series, and, USBR CVO Water Accounting Reports all explicitly state quantities as pumped through Banks. DWR SWP Capability Reports and Bulletin 160 Water Plan Updates provide values as total SWP deliveries, so subtracting North Bay Aqueduct and Feather River deliveries should be volumes pumped through Banks. DAYFLOW estimates are inflows into Clifton Court Forebay to Banks Pumping Plant.

Why are the values different? Specifically, why do these values match closely in 2006 and differ so much by 2010?  Inquiries and data references were unable to answer those questions. Perhaps some water transfers are not counted as SWP deliveries (including, CVP-related transfers through Banks).  Perhaps some pumping from Banks is counted as deliveries for other projects.  Some small differences occur for DAYFLOW between water entering Clifton Court Forebay and water pumped through Banks.

Although there are technical challenges to water accounting, the challenge of water accounting is more organizational than financial or technical.  California’s current water accounting systems have difficulty presenting a transparent, well documented, and consistent accounting of water availability and use.  This seems to apply even to some of the largest, most centrally controlled, and technically easiest flows in the system, such as Banks Pumping Plant.

Poor organization makes water management in California unnecessarily more difficult, controversial, opaque, and expensive. Propagation of volume differences from the many pumping plants, canals, and other water infrastructure in California only exacerbates this situation. We are paying several costs for many watches.

Further Reading

Alvar Escriva-Bou, Henry McCann, Ellen Hanak, Jay Lund, Brian Gray (2016), Accounting for California’s Water, Public Policy Institute of California, San Francisco, CA.  (The technical appendix is especially useful for showing how other states and countries organize their water accounting.)